On cold days after you haven't driven your Boxster in several days, do you get wheel hop? It's like my tires feel out of round and the steering wheel vibrates. This will smooth out over the course of several miles and is gone in say 15 miles...

I have 17" Continentals.

Has anyone tried any of the various products on the market to prevent "flat spots"?

I can definitely feel this. But like you said it goes away fairly quickly with driving.

I think there are two kinds of flat spots, one which is the simple creasing of the rubber from the car sitting on them, the other which involves some kind of thermal distortion. This later kind is basically impossible to get in street driving (involves putting a 200 degree tire on cold concrete and leaving it there as the rubber cools), but it is the kind which the "Tire Cradle" product has the "measurable research" on. Besides which the Tire Cradle is ridiculously priced.

I was going to go with some product like the Tire Cradle for winter storage, but after I learned more I decided to hedge my bets and just store the car with 50 psi in each tire. I left it up to 4 weeks between drives, and never had any issues except for the usual initial vibration like you describe.

Hi rob,
As Charlie stated, the initial vibration quickly dissipates; all three of my tire varieties have done it, but the most noticeable were the original Contis. I don't know if it was something peculiar to the compound or the effects of "age" but they certainly were bouncy for a few miles particularly after sitting idle for a few cold nights. You may recall that I am running 18s, so the effect may be more apparent than on 17s.

Interestingly enough, I bought a set of the "ridiculously priced" Tire Cradles shortly after I got the car, in my naivete, to avoid flatspotting; maybe they work as proposed since the vibration is so transient -- more likely, as Charlie alluded to, current technology makes permanent flatspotting from short-term storage a non-issue. I still have the cradles on my garage floor, but they serve more as car positioning markers than anything else.